The present invention relates generally to a manner by which to facilitate communication of a data block to a mobile station in which communications with the mobile station are handed off from a first target entity to a second target entity. More particularly, the present invention relates to apparatus, and an associated method, for transferring a portion of the data block, previously delivered to the first target entity, but not yet affirmed to have been successfully communicated to the mobile station, to the second target entity. Other portions of the data block, not yet delivered to the first target entity are provided directly to the second target entity to be communicated therefrom to the mobile station. Improved communication rates are provided without requiring a high bandwidth link between the first and second target entities.
A communication system is formed, at a minimum, of a sending station and a receiving station interconnected by a communication channel. Data is communicated by the sending station to the receiving station by way of the communication channel. The data is converted, if necessary, into a form to permit its communication upon the communication channel. And, when received at the receiving station, the informational content of the data is recreated to permit use to be made of the data at the receiving station.
In a communication system in which the communication channel is formed of a radio channel defined upon a portion of the electromagnetic spectrum, the communication system is referred to as a radio communication system. A wire line connection is not required to interconnect the sending and receiving stations. In contrast to a conventional wire line system, communications are effectuable through the use of a radio communication system even when a wire line connection cannot be conveniently formed between the sending and receiving stations.
A cellular communication system is an exemplary type of radio communication system. Various cellular communication standards have been promulgated, and cellular communication systems have been implemented pursuant to such promulgated standards. And, additional cellular communication systems continue to be proposed. Improvements to existing cellular communication systems have similarly also been proposed.
A cellular communication system is implemented throughout a geographic area by positioning a plurality of fixed-site, base transceiver stations at spaced intervals throughout the area in which the communication system is to be implemented. Each of the base stations defines a coverage area, referred to as a cell, within which radio communications with a mobile station are possible. The base stations are controlled by cell gateways (CGWs), and the cell gateways are connected to a base station gateway (BSGW). The base stations, CGWs and BSGWs, are collectively referred to as the network infrastructure. A mobile station is used to communicate, by way of a radio link, with a selected base station. The mobile station typically is movable throughout the geographic area in which the communication system is implemented. The mobile station might initially, therefore, be positioned in a first cell, referred to as a serving, or source, cell and thereafter be repositioned in another cell, referred to as a target cell. Handover of communication with the mobile station from the base station encompassing the source cell to the base station encompassing the target cell permits continued communication with the mobile station.
While cellular communication systems were generally first implemented to communicate data using analog communication techniques, increasingly, cellular, and other, communication systems are constructed to permit communication of data utilizing digital communication techniques.
When digital communication techniques are used, typically, the data to be communicated is first formatted into one or more data frames. The data frames are then communicated. For instance, data originated at, or at a device coupled to, the network infrastructure is formatted into one or more data frames and then sent by way of a radio link to the mobile station. Formatting, or other segmentation, of the data is performed at the network infrastructure and, once formatted or otherwise segmented, the data is sent by a source base transceiver station to the mobile station. When frame-formatted data is communicated, certain of the communication systems utilize an acknowledgment scheme, such as an ARQ scheme. In an ARQ scheme, a receiving station acknowledges receipt of data with an affirmative acknowledgment (ACK) of successful communication of the data or a negative acknowledgment (NACK) indicating unsuccessful completion of communication of the data.
Problems with communication of such frame-formatted data in a mobile communication system which uses an ARQ scheme, or other similar scheme, might occur. When a handover of communications from a first target entity to a target entity is effectuated during the time period in which a block of data is in the process of being sent to the mobile station, a portion of the data block may not have been affirmed to have been successfully delivered to the mobile station. This portion of the data block must be recommunicated to the mobile station by the target entity subsequent to handover of communications thereto. If the location at which the data is formatted, or otherwise segmented, is located together with the first target entity from which the data is communicated to the mobile station prior to the handover, a significant amount of data would regularly have to be forwarded from the first target entity to the second target entity upon handover of communications.
A high-speed data link would need to be installed between the first and second target entities to ensure that the data is timely forwarded to the second target entity.
If a manner could be provided by which to provide a manner by which better to forward data to a second target entity pursuant to handover of communications to the second target entity, improved communication rates, without the use of a high-speed datalink, would be possible.
It is in light of this background information related to the communication of data in a mobile radio communication system that the significant improvements of the present invention have evolved.
The present invention, accordingly, advantageously provides apparatus, and an associated method, by which to facilitate communication of a data block to a mobile station in which communications with the mobile station are handed off from a first target entity to a second target entity.
Through operation of an embodiment of the present invention, a manner is provided by which to transfer a portion of the data block, previously delivered to the first target entity, but not yet affirmatively communicated to the mobile station, to the second target entity. Other portions of the data block, not yet delivered to the first target entity, are instead routed to the second target entity pursuant to the handover of the communications to the target entity.
In one aspect of the present invention, a mobile communication system is operable to communicate a data block of digital data to a mobile station. The data block is segmented by a segmentation unit which is located at a device other than the first target entity and the second target entity. Because the segmentation unit is positioned separate from the first target entity, when a handover is effectuated during communication of the data block to a mobile station, only portions of the data block, already delivered to the first target entity and not yet acknowledged or not yet transmitted, need to be routed from the first target entity to the second target entity. Thereby, lesser amounts of data are required to be transferred between the first and second target entities pursuant to a handover of communications. The need otherwise to use a high-speed data link between the first and second target entities to ensure timely forwarding of the data is obviated.
In another aspect of the present invention, a segmentation and distribution unit (SDU) is positioned at a base station gateway (BSGW), thereby to be positioned separate from both a first target entity and a target entity, such as a source cell gateway and a target cell gateway. The SDU is operable to segment the data block according to a selected segmentation scheme. Once segmented, the data block is forwarded, portion-by-portion, to the first target entity. When a handover of communications is effectuated from the first target entity to the second target entity, remaining portions of the data block, not yet forwarded to the first target entity, are instead forwarded to the second target entity. Because the data block is forwarded on a portion-by-portion basis to the first target entity and only un-acknowledged or not-yet-transmitted data needs to be forwarded to the second target entity, the amount of data which must be forwarded by the first target entity to the second target entity pursuant to a handover of communications is likely to be less than if all of the data block had been forwarded to the first target entity.
In another aspect of the present invention, portions of the data block forwarded to the first target entity are buffered at a buffer, thereafter to be communicated from the first target entity, such as from a base transceiver station (BTS) thereof to the mobile station. When the data is successfully communicated to the mobile station, and acknowledgment is returned to the first target entity pursuant to a conventional acknowledgment scheme, such as an ARQ acknowledgment scheme. The portions of the data buffered at the buffer remain buffered thereat until a positive acknowledgment is returned by the mobile station indicating successful communication of the portion of the data to the mobile station. As the indications of the successful completion of the communication of the data to the mobile station are detected at the first target entity, such data is no longer required to be buffered at the buffer.
When a handover of communications is initiated, such as pursuant to a MAHO (mobile-assisted handover) procedure, data remaining at the buffer includes data not yet communicated to the mobile station or data not affirmatively acknowledged to have been delivered successfully to the mobile station. Such data is provided to a data forwarder to be forwarded therefrom to the second target entity. Once delivered to the second target entity, the data remains available for retransmission to the mobile station, if necessary.
In one implementation, the mobile communication system is operable generally pursuant to a CDMA 2000 (code-division, multiple-access 2000) standard specification which provides for the communication of digital data using an ARQ acknowledgment scheme pursuant to 1XTREME operation. A segmentation and distribution unit (SDU) is positioned at a base station gateway, separate from, and coupled to, a first target cell gateway and a second target cell gateway. A data block to be communicated to a mobile station operable in the communication system is segmented by the SDU. Portions of the data block, once segmented, are forwarded to a first target cell gateway. The portions forwarded to the first target cell gateway are buffered at a buffer of the first target cell gateway and subsequently communicated to the mobile station. When a handover of communications is to be effectuated during a communication session in which the data block is in the process of being communicated to the mobile station, portions of the data block buffered at the first target cell gateway are forwarded to the second target cell gateway. Data portions of the data block not previously delivered by the base station gateway to the first target cell gateway are routed directly to the second target cell gateway. Because the SDU and the first and second target cell gateways are located at separate entities of the network infrastructure, reduced amounts of data need to be forwarded by the first target cell gateway to the second target cell gateway. And, as a result, high speed data lines interconnecting the first and second target cell gateways are obviated.
In these and other aspects, therefore, apparatus, and an associated method, are provided for a mobile communication system having a mobile station and a network portion. The network portion has a first target entity and a second target entity. The mobile station at least receives a data block sent by the network portion to the mobile station pursuant to a communication session. A portion of the data block is transferred from the first target entity to the second target entity, thereby to permit communication of the data block to the mobile station when a communication handover is effectuated from the first target entity to the second target entity. A first target-entity buffer is positioned at the first target entity. The first target-entity buffer buffers the portion of the data block at the first target entity at least prior to successful delivery of the portion of the data block to the mobile station. A data forwarder is positioned at the first target entity. The data forwarder is coupled to the first target-entity buffer and to the second target entity. The data forwarder forwards the portion of the data block to the second target entity upon effectuation of the communication handover to the second target entity.
A more complete appreciation of the present invention and the scope thereof can be obtained from the accompanying drawings which are briefly summarized below, the following detailed description of the presently-preferred embodiments of the invention and the appended claims.